1911] Grinnell: The Linnet of the Hawaiian Islands. 189 



is almost if not quite exclusively a feeder upon vegetable mater- 

 ials (seeds and fruits). In its wide range over the North Ameri- 

 can continent, in most parts of which it is non-migratory, it 

 inhabits very many diverse floral areas productive of foods of 

 great variety. As far as the data go (Table I) the occasional 

 yellow sports do not occur with preponderating frequency in any 

 one floral area. If this is the case over the continent, it is hardly 

 to be expected that there could be any food of extraordinary 

 qualities occurring in quantity in the several separate island 

 habitats, and there alone, that would have brought about the 

 same peculiarities of color. 



The theory has been advanced (Keeler, 1893, p. 154) that 

 in the evolution of color phylogenetically yellow is a primitive 

 one, and that red is a later development. A fact in support of 

 this idea is the ontogenetic condition frequent among birds, 

 where the young are yellow, the adult males, at least, red. This 

 is quite in harmony with the color formation theory of Riddle. 

 But that the occurrence of occasional yellow examples among the 

 linnets of California may be considered reversionary, is not so 

 apparent. In the case of the linnet, the young are without any 

 bright colors at all. The first color to appear in the lifetime of 

 the individual of the California linnet is, normally, red. 



We find that linnets introduced on the Hawaiian Islands, 

 where they have perfect freedom, abundant food-supply, and 

 such all-round favorable environs that they have multiplied and 

 spread prodigiously within a relatively short time, have acquired 

 color characters similar to birds in confinement. If deteriora- 

 tion in vigor contributes to the decoloration of the latter, it does 

 not appear clear how the same cause could be held to have 

 accounted for the former. Even if the linnets introduced on the 

 Islands are actually subject to much more favorable conditions 

 (lack of enemies, more abundant food-supply, etc.), it is not 

 clear to me how this new environmental condition would neces- 

 saril.y result in deterioration in physical vigor. It would appear 

 from a survey of distributional' behavior in appropriate cases 

 among North American birds, that where one or more adverse 

 factors are withdrawn the species reacts simultaneously by in- 

 crease in numbers until some other check or checks become 



